Space–time evolution of monogenetic volcanism in the mafic Garrotxa Volcanic Field (NE Iberian Peninsula)

Abstract

27We reconstructed the evolution of the volcanic activity within the central 28 Garrotxa monogenetic Volcanic

Volcanic stratigraphy of the Quaternary La Garrotxa Volcanic Field (north‐east Iberian Peninsula)

“…However, we observed no structural indicator that could suggest a similar tendency in the Neogene faults as suggested by Cimarelli et al . (). Some of the eruptions developed in multiple phases and with multiple vents along the same eruption fissure (Martí et al ., ), and are thus responsible for some of the clusters of vents that appear in Fig.…”

“…When the source area or vent of the different volcano‐stratigraphic units or members was plotted on a structural map of the area with the successive numbers of their relative ages (1 for the youngest, 55 for the oldest) indicated (Fig. ), it becomes evident that most members are located on NNW–SSE‐orientated Neogene fractures and faults, thereby confirming the findings of other authors (Martí et al ., ; Cimarelli et al ., ; Barde‐Cabusson et al ., ; Bolós et al ., ). These members have a rather scattered time–space distribution, albeit with a tendency for older eruptions (Middle Pleistocene) to be concentrated towards the north of the area.…”

“…The use of ephemeral outcrops, wells and boreholes (this work), in combination with results from the application of shallow geophysical methods (Bolós et al ., , ; Barde‐Cabusson et al ., , ), allowed us to obtain the volcanic stratigraphy of the highly urbanized – and, consequently, with a poorly exposed geology – area of Olot (Fig. ), thus improving previous maps (Mallarach, ; IGC (Institut Geològic de Catalunya), , ; Cimarelli et al ., ) that could not show the same degree of detail. In this sector of the GVF we found very complex stratigraphic relationships between the city's five volcanic cones (Garrinada, Montsacopa, Bisaroques, Ca l'Isidret and Montolivet) (Fig.…”

“…This new volcano‐stratigraphic framework complements a previous study focused on the description of the successions of deposits characteristic of the GVF volcanoes (Martí et al ., ), and improves the recent stratigraphy proposed by Cimarelli et al . (), which is based on different stratigraphic criteria (synthoms) and is partially incomplete due to the lack of subsoil information and that from the ephemeral outcrops. Table summarizes all the stratigraphic members (55 in all) that were identified in this study.…”

“…The eruptive fissures that controlled the volcanic activity in the GVF correspond to NNW–SSE and NNE–SSW orientated Neogene tectonic structures (Cimarelli et al ., ; Barde‐Cabusson et al ., , ; Bolós et al ., ). This suggests that the ascent and eruption of the magmas originated at the base of the lithosphere (Martí et al ., ) and was guided by the same regional fault system that bound the area's horsts and grabens.…”